Fix crash in VisualBasic.Binder.MemberLookup.AddLookupSymbolsInfoInTypeParameter when it is called with Cref TypeParameter. (#21586)

Fixes https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=410932.

The fix mimics the way C# compiler handles Cref TypeParameters in the similar API.

are marked not usable in C#7

* Compare lines instead of using AssertXml when validating PDBs.

AssertXml doesn't validate ordering.

* Reorder expected PDB XML nodes to match actual order

* Update to the latest Microsoft.DiaSymReader.* packages.

* Enable embedding sources to Windows PDBs

* Tagging VB/C# Ioperation tests

* Fix the Wrong Tagging

* Adding ioperation tests for WhileUntilLoopStatement

* Addressing Feedback

* Removing redundant Nested tests

* Removing the empty lines

* Rename Foo to Goo

* Rename ifoo to igoo

* Add back BOMs

* Expose if a Binary/Unary operator was 'Lifted' at the IExpression level.

* Update public API.

* Share computed value.

* Remove unnecessary extension.

* Update test code.

* Remove extension method.

* Fixup tests.

* Fixup tests.

* Fixup tests.

* Fix instances of Invalid operations with nullable

* Compound assignments also need to state if they're lifted.

* Move tests.

* Move tests.

* Move tests.

* Simplify comment.

* Case things consistently.

* Use F instead of Foo.  Because Foo is bad.

Fixes #20693

* Adding ioperation tests for ForEachStatement

* Addressing Feedback

* Removing Yield and nested tests

* Addressing PR feedback

* Fix breaking unit tests

This changes our core Roslyn.Test.Utilities project to use
multi-targeting to control how we create our core compilation helper.
Previously this was done by having a separate runtime specific assembly
which was probed at runtime.

The intent of this change is to make our build more correct here. I can
now target just Roslyn.Test.Utilties with a net46 framework and get a
runnable asset out of it. This is necessary in order for our unit tests
to successfully run when moved to multi-target.

Presently this makes it multi-target across net46, netcoreapp2.0 and
netstandard1.3. The impl in netstandard 1.3 simply throw for this
specific API. Over the long term it make make sense to pull this out to
a separate library that only targets net46 + netcoreapp2.0. That
requires a much deeper investment in multi-targeting though. Decided to
start smaller for now.

expose Root from SemanticModel
shared same test methods between C# and VB
removed DEBUG region and used foreach
added clone test for c# and vb
use ArrayBuild as Stack

This required changing CurrentVersionNumber to a property.

* Adding ioperation tests for ForloopStatement

* Addressing the feedback

* Changing the dumper to get of calling base.Visit when not needed

* Getting rid of cobyrc file

* Adding copyright header

* fixing merge conflict